Fig. 4

The ROC analysis indicated that STAD was a reliable measurement in predicting cut-out (Area under the curve (AUC) = 0.864, p < 0.001), of which the best cut-off value was 2.92D (Sensitivity = 73.3%, specificity = 91.7%) (A). In comparing STAD with TAD, there was no significant difference on predicting cut-out between STAD and TAD (STAD, AUC = 0.864; TAD, AUC = 0.775; p = 0.08) (B). However, “STAD > 3D” was observed with good predicted effect of cut-out (AUC = 0.806, p < 0.001) (C). In comparing “STAD > 3D” with “TAD > 25 mm”, significant difference of cut-out was found in “STAD > 3D” (“STAD > 3D”, AUC = 0.806; “TAD > 25 mm”, AUC = 0.659; p = 0.047) (D)